KR101498410B1 - Alumina conjugate and bonding method for alumina sintered bodies - Google Patents

Abstract

And the alumina sintered bodies are bonded via the joints. Wherein the joint portion is made of alumina having a thickness of 30 占 퐉 or more and has a coarse independent pore having a hole diameter in the thickness direction of 40 to 100% of the thickness of the joint portion, An alumina bonded body formed of a fine-grained region including fine pores and a dense sintered region having a relative density of 98% or more.

Description

Technical Field [0001] The present invention relates to a method for joining an alumina bonded body and an alumina sintered body,

The present invention relates to a method of joining alumina sintered bodies bonded with alumina sintered bodies and a method of joining alumina sintered bodies, and more particularly, to an alumina joined body capable of being applied to a large member having a length of several meters and satisfying high purity and high strength requirements, To a method of joining an alumina sintered body for manufacturing the same alumina joined body.

Recently, in order to improve quality and productivity in various manufacturing fields, engineering ceramic members used for production are required to be large-sized and high-purity. Particularly, it is difficult to cope with the conventional integrated ceramic molding / firing technique in the production of a large member of several meters. Therefore, it has become necessary to develop a technique for fabricating a desired member by joining a plurality of small ceramics sintered bodies (blocks) by manufacturing and combining them, and locally heating only the portions to be joined. In addition, in semiconductor manufacturing apparatuses and chemical plants requiring heat resistance and corrosion resistance, the incorporation of impurity elements into products is strictly restricted, and a member having a high purity is required for use. Particularly, in a large-sized ceramics pipe (pipe member) used as a constituent member of a rotary kiln used for manufacturing a positive electrode material for a lithium ion secondary battery, it has high purity, high high temperature strength, Cm and a length of up to 5 m.

Conventional methods of joining ceramics sintered bodies include an oxide solder method and a high-melting-point metal method. However, these joining methods are not preferable for the above-mentioned applications because of incorporation of impurity elements and deterioration of high-temperature strength. In addition, it is difficult to apply a high pressure to the material to be bonded during heating, as in the case of the solid-phase pressure bonding method, and it is difficult to manufacture a large-sized member.

On the contrary, as a joining method in which ceramics sintered bodies are bonded without pressurization and the resulting bonded body can maintain high purity, a technique of bonding and fusing ceramics particles having the same composition as that of the ceramics sintered body using a slurry in which pure water is dispersed (See Patent Document 1).

However, in the bonding method described in Patent Document 1, in addition to the problem that the bonding strength is less than 100 MPa and the bonding strength is insufficient, the thickness of the bonding layer is as small as 0.5 탆 and it is not applicable to bonding of a large member . This is because the surface to be bonded of the ceramics sintered body (block) used for joining for manufacturing a large-sized member is, for example, larger than several tens of centimeters in diameter in the case of a tubular sintered body, This is because it is generally difficult to complete the bonded surface at a flatness of about 0.1 탆 at maximum, which is considered to be necessary for the bonding method described in the above-mentioned Patent Document 1. This is because the manufacturing cost is too high to be practical. In this way, it is not preferable from the viewpoint of manufacturing cost to finish the section of the large ceramics sintered body with high precision by grinding. Therefore, a bonding method which can tolerate even the irregularities of the surface to be bonded of several tens of micrometers is required.

As another joining method, in the joining of the beta alumina tube and the ceramics tube, an alumina slurry is applied as an insert material to the surface to be bonded to a thickness of about 0.2 mm, the both tubes are brought into contact with each other and dried, and then the joining material is obtained by microwave heating (See Patent Document 2).

However, the bonding method described in Patent Document 2 is a special method in which application to beta alumina, which absorbs microwaves is large, is limited. As the structural ceramics, alpha-alumina is generally used, and since the absorption of the microwave is very small, heating by microwave is generally difficult. If it is desired to heat by microwave, it is necessary to add an impurity which absorbs microwaves well. However, in this case, the alumina bonding member becomes not high purity. In addition, since heating by microwave can not use a thermocouple, it is difficult to measure the temperature and the temperature of the material to be bonded can not be precisely controlled. Therefore, there is a fear of damaging the material to be bonded due to unexpected heat generation, It can not be done. In addition, in Patent Document 2, there is no description of bonding strength, and considering the above problems, it is doubtful whether the bonding strength can be stably obtained. Even if a bonded body can be obtained, It is easy to assume that the imbalance of the measured values was large.

Further, in the bonding method described in Patent Document 2, in order to uniformly heat, the material to be bonded is rolled at ten revolutions per minute in the microwave sintering apparatus in the state that the raised stone is placed thereon. However, the sintered body of large ceramics is sintered by microwave It is technically difficult to rotate under the same conditions in the apparatus. From these problems, this method is not practical as a method of joining a large-sized alumina sintered body which requires high purity.

As the present state, there is no high-strength bonding method of a sintered compact of high-purity alumina capable of maintaining a high purity. Therefore, the large-sized ceramic pipe for a rotary kiln may be a pipe made of porous ceramics, A pipe made of a sintered body is merely sold as a large pipe which is housed in a frame having a special structure and mechanically connected by compressive stress from both ends. However, in the case of the former, there is a problem that the porosity is as high as about 25% and the bending strength is only about 8 MPa at the maximum, so that it can not withstand high stress. In the latter case, there is a problem that there is a step on the joint or that the apparatus is complicated and large-scale.

JP 2010-18448 A JPH8-59358A

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problem, and it is an object of the present invention to provide a bonding material which has high bonding strength and excellent corrosion resistance, can be configured so that the bonding portion does not contain impurities, And a constituent member of a rotary kiln for use in the production of a positive electrode material for a lithium ion secondary battery, which comprises the alumina joined body and the alumina joined body which can be suitably applied to a large member having a high tolerance to flatness And a method of joining the alumina sintered body with the alumina sintered body which can be produced by heat treatment under reduced load.

In order to achieve the above object, there is provided a method of joining the following alumina joined body, tubular member and alumina sintered body according to the present invention.

[1] An alumina bonded body in which alumina sintered bodies are bonded via a bonding portion, wherein the bonding portion is made of alumina having a thickness of 30 탆 or more, and the hole diameter in the thickness direction of the bonding portion is 40 to 100% And a dense sintered region having a relative density of 98% or more. The alumina bonded body according to claim 1,

[2] A bending strength at room temperature of 200 MPa or more as measured in accordance with JIS R1601 using a test piece cut from the alumina bonded body to include the abutment portion and a flexural strength at 1200 ° C measured in accordance with JIS R1604 Is 100 MPa or more.

[3] A pipe member made of an alumina bonded body according to [1] or [2], wherein the dense alumina sintered bodies having a relative density of 95% or more are bonded through the bonding portion.

[4] A pipe member according to [3], which is used as a constituent member of a rotary kiln used for manufacturing a positive electrode material for a lithium ion secondary battery.

[5] A method for bonding an alumina sintered body to which alumina sintered bodies are bonded, comprising preparing an alumina slurry containing pure water added with a dispersant as a dispersion medium and adding only alumina particles having a purity of 99.8% After the slurry was applied to the bonded surface of the alumina sintered body, the bonded surfaces were brought into contact with each other to adjust the thickness of the bonded portion made of the alumina slurry to be sandwiched between the bonded surfaces to be 30 占 퐉 or more to prepare a bonded body , The bonded body is subjected to a heat treatment in the atmosphere at a temperature of from 1300 DEG C to 1700 DEG C under a load so that the surface pressure of the bonded surface is 0.015 MPa or more to sinter the bonded portion, A method of joining a sintered body.

[6] The method for bonding an alumina sintered body according to [5], wherein the content of alumina particles in the alumina slurry is 65 mass% or more and less than 77.5 mass%.

The alumina joined body of the present invention can form a bonded portion by sintering in air without heating by microwave, as in the bonding method of the alumina sintered body of the present invention described later. Therefore, It is not necessary to add the alumina sintered body to be bonded, and the alumina sintered body to be bonded, as well as the joint portion to which the alumina sintered body is bonded, can be constituted only by high purity alumina. Therefore, the alumina bonded body of the present invention exhibits high bonding strength and excellent corrosion resistance without deterioration of corrosion resistance and strength due to the impurities remaining in the joint, and there is no fear of contamination by impurities. Therefore, the alumina bonded body of the present invention can be widely applied to various large structural members, and is particularly useful for production of semiconductor manufacturing apparatuses and chemical plant members, which are required to be composed of a high-purity material free from the risk of incorporation of impurity elements And can be suitably used as a large member to be used. The alumina bonded body of the present invention can absorb the irregularities even if the flatness of the end surface (bonded surface) of the bonded material is several tens of micrometers because the thickness of the bonded portion is 30 占 퐉 or more, It may deteriorate the requirement for finishing the work. In other words, since it is not necessary to perform high-precision machining on a large-sized bonded material, even a large bonded body can be manufactured at low cost. In addition, as described above, the joining portion having a margin in the thickness absorbs the unevenness of the joining surface, so that joining at the entire surface to be joined can be performed, and high joining strength is exhibited. Further, as described above, since the bonding portion can be formed only with high purity alumina and can not contain impurities such as glass, the bonding strength can be maintained even at a high temperature environment of 1200 占 폚 and application to applications requiring heat resistance .

The tubular member of the present invention is applied to a tubular member which is one of typical applications of the alumina joined body of the present invention. This tubular member exhibits the effect of the alumina joined body of the present invention as described above. Therefore, the tubular member can be used as a large structural member requiring particularly high purity and high strength, for example, a rotary member used for manufacturing a positive electrode material for a lithium ion secondary battery It can be suitably used as a constituent member of a kiln.

According to the method for bonding an alumina sintered body of the present invention, the alumina bonded body of the present invention having the above-described excellent effects can be produced. The method of bonding an alumina sintered body of the present invention can bond a sintered alumina body to be bonded by heat treatment in an atmospheric air at low cost to a large hot press furnace, And can be joined by a common air atmosphere furnace.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an example of an alumina joined body of the present invention and a schematic structure of a bonded body which is a precursor thereof.
2 is a SEM photograph of a cross section of a bonded portion of the alumina bonded body of the present invention.
3 is an optical microscope photograph of the junction of the alumina junction body of Comparative Example 2;

The present invention will now be described based on a specific embodiment, but the present invention is not construed as being limited hereto, and various modifications, corrections and modifications may be made without departing from the scope of the present invention, , And an improvement can be added.

The alumina joined body of the present invention is characterized in that the alumina sintered bodies are bonded to each other through a joining portion and the joining portion is made of alumina having a thickness of 30 占 퐉 or more and the hole diameter in the thickness direction of the joining portion is 40 to 100% Length micro pores having a diameter of 5 mu m or less and a dense sintered region having a relative density of 98% or more.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an example of a ceramics bonded body of the present invention and a schematic structure of a bonded body which is a precursor thereof; FIG.

The ceramics bonded body of the present invention having the above characteristics can be manufactured according to the method of bonding the alumina sintered body of the present invention.

In the method of bonding an alumina sintered body of the present invention, pure water added with a small amount of a dispersant is used as a dispersion medium, and only alumina particles having a purity of 99.8% or more are added to the dispersion medium as solids and mixed and stirred to prepare an alumina slurry . Here, if a sintering auxiliary agent or the like is added as a solid component, impurities remain in the joint portion, which causes deterioration of corrosion resistance, deterioration of high-temperature strength, contamination by impurity elements, and the like. As the dispersant, for example, a polycarboxylic acid ammonium salt or the like can be used. Further, when a dispersant is not added to pure water, it is difficult to add alumina particles at a high concentration in a state of fluidity, and it is difficult to obtain a bonded portion having a high bonding strength.

The content of alumina particles in the alumina slurry is preferably more than 65 mass% and less than 77.5 mass%. When the alumina content in the alumina slurry is 65% by mass or less, large voids are formed in the joint due to evaporation of water during drying of the alumina slurry, which may cause a decrease in strength. On the other hand, when the alumina content in the alumina slurry is 80% by mass or more, the alumina slurry becomes insufficient in fluidity, and the slurry can not be uniformly applied to the entire surface to be bonded, resulting in bonding unevenness. In addition, although the slurry can be applied uniformly at 77.5 mass%, as shown in the photograph of the optical microscope in Fig. 3, cracks 30 are generated between the joint portion and the surface to be bonded, I do not. The mechanism of formation of the crack 30 is not clear, but it can be considered as one factor that the surface of the slurry is dried after coating to form a film, which hinders adhesion between the surface to be bonded and the slurry.

Subsequently, the prepared alumina slurry is applied to both the bonded surfaces of the alumina sintered bodies 1a and 1b or the bonded surfaces of the other alumina sintered bodies 1a and 1b and the bonded surfaces of the alumina sintered bodies 1a and 1b are brought into contact with each other, (Bonding portion before sintering) 2 made of the above-mentioned alumina slurry interposed between the surfaces is adjusted to be 30 m or more to prepare a joined body 1A. If the thickness of the joint is less than 30 占 퐉, there is a possibility that the alumina sintered bodies 1a and 1b will not be bonded without absorbing irregularities on the bonded surfaces. Although the upper limit of the thickness of the joint portion is not particularly limited, if the thickness of the joint portion is excessively large, the size of the coarse independent pores formed in the joint portion becomes too large and the joint strength may become insufficient. It is preferable that the thickness is 100 mu m or less.

Then, the prepared bonded body 1A is heat-treated in the atmosphere. By this heat treatment, the bonded portion 2 of the cemented carbide body 1A is sintered and the alumina bonded body 1B of the present invention in which the sintered alumina sintered bodies 1a and 1b are joined together by the bonded portion 3 after sintering is obtained. This heat treatment is carried out with the load applied so that the surface pressure of the surface to be bonded is 0.015 MPa or more, preferably 0.015 to 0.030 MPa. When the surface pressure of the surface to be bonded at the time of the heat treatment is less than 0.015 MPa, cracks of up to several hundreds of micrometers occur between the bonding portion and the surface to be bonded, and the bonding strength deteriorates. The surface pressure of the bonded surface can be adjusted by, for example, arranging the bonded body 1A such that the alumina sintered bodies 1A and 1B are vertically aligned as shown in FIG. 1, Can be carried out by putting a rolling stone of a mass. As the raised stone, for example, an alumina sintered body can be suitably used. Further, when the alumina sintered body 1a is caused to exert a surface pressure of 0.015 MPa or more on the surface to be bonded only on the basis of its own weight, there is no need to exert loads from the outside such as raised stones. For example, when a rectangular parallelepiped or cylinder of an alumina sintered body having a length of about 1 m is vertically stacked and bonded to each other, the surface pressure of a surface to be bonded which is generated by the magnetic weight of the alumina sintered body is about 0.04 MPa. It is possible to obtain a bonded body having sufficient strength without exerting a load from the outside. The heat treatment under such a reduction can be carried out by using an ordinary atmospheric furnace.

This heat treatment is performed at a temperature of 1300 ° C or higher and 1700 ° C or lower. When the heat treatment temperature is less than 1300 ° C, sintering of the alumina powder at the joint does not proceed sufficiently and sufficient joint strength can not be obtained at the joint. On the other hand, if the temperature exceeds 1700 占 폚, the grain growth of the sintered body may occur and the mechanical properties of the base material may deteriorate.

When the surface pressure of the surface to be bonded and the heat treatment temperature are set as described above and heat treatment is performed, the bonding portion 2 made of the alumina powder of the joined body 1A has a volume (volume) due to sintering of the alumina powder And the densification progresses. However, since the alumina sintered bodies 1a and 1b to be bonded do not shrink, the densification does not proceed in other regions but becomes a microstructure area, leaving many fine pores. Further, due to the contraction of the densified area as described above, the joining portions are drawn in the horizontal direction in other regions, and coarse independent pores are formed in the joining portion. As a result of this heat treatment, the joint portion 2 made of the alumina powder of the joined body 1A has the coarse independent pores 20c having a hole diameter of 40 to 100% of the thickness of the joint portion in the thickness direction of the joint portion, The bonding portion 3 is formed as a dense sintered region 20b having a relative density of 98% or more in the untreated region 20a including micropores having a diameter of 5 占 퐉 or less. The bonding portion 3 is a sintered body of alumina (1B) of the present invention is obtained.

2 is an SEM photograph of a cross section of a bonded portion of the alumina bonded body of the present invention. In this photograph, the bonded portion 3 has (1) fine-grained areas 20a and 2 (3) a coarse pore having a hole diameter in the thickness direction of 40 to 100% of the thickness of the joint portion 3 20c, respectively. The bonding portion 3 and the upper and lower alumina sintered bodies (materials to be bonded) are in close contact with each other in the unhardened region 20a and the sintered region 20b and no cracks or the like are observed at the bonding interface. It is understood that the sintered body is responsible for the bonding.

In addition, a plurality of coarse independent pores 20c are present in the joint portion 3, so that a part of the surfaces to be bonded does not have an unbonded region where they are not bonded. However, these coarse independent pores 20c are not connected to each other Therefore, the formation of large cracks does not occur, and the deterioration of the joint strength due to the presence of the coarse independent pores 20c is not large. In the heat treatment, the joining portion is allowed to shrink in the horizontal direction (direction perpendicular to the thickness direction of the joining portion). Since it is not necessary to largely contract in the vertical direction (thickness direction of the joining portion), the sintering region 20b ) And the uncontaminated region 20a, generation of sharp cracks in the joining portion 3 in the horizontal direction is suppressed, and the bonding strength is not greatly deteriorated.

As a result, the alumina bonded body of the present invention exhibits high strength. Specifically, the strength of not less than 200 MPa can be exhibited as the bending strength at room temperature measured in accordance with JIS R1601 by using a test piece cut from the alumina joined body of the present invention including the joint portion. Further, the flexural strength in air at 1200 DEG C measured in accordance with JIS R1604 can exhibit a strength of 100 MPa or more.

The tubular member of the present invention is a tubular member made of the alumina joined body of the present invention, and has a bonded structure in which dense alumina sintered bodies having a relative density of 95% or more are bonded through the above-mentioned bonded portion. This tubular member is applied to the tubular member which is one of typical applications of the alumina joined body of the present invention. This tubular member is made of alumina sintered body to be bonded and has a relative density of not less than 95%. In addition, since the alumina bonded body of the present invention exhibits the effect as described above, It can be suitably used as a structural member, for example, as a constituent member of a rotary kiln used for producing a positive electrode material for a lithium ion secondary battery.

(Example)

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

(Examination of alumina content in alumina slurry)

A commercially available alumina sintered body having an alumina purity of 99.5% or more and a relative density of 99.0% or more was processed to 20 mm x 16 mm x 5 mm, and a test piece obtained by grinding a 20 mm x 16 mm surface with # 200 abrasive wheels Prepared. A cell and D305 (trade name) manufactured by Nakagyo Kyoeisha Kogyo Co., Ltd., having a polyacrylic acid ammonium salt as a main component as a dispersant, were added to pure water so as to have a mass ratio of 17: 1 and stirred well to prepare a dispersion medium. With respect to this dispersion medium, alumina particles having a purity of 99.8% or more and an average particle diameter of 600 nm were dispersed in an aqueous solution containing 65.0 mass%, 69.5 mass%, 74.5 mass%, 77.5 mass% and 80.0 mass %, And the mixture was stirred to obtain a slurry in which alumina particles were dispersed and mixed in a dispersion medium. Further, this slurry was vacuum degassed by using a vacuum pump for about 2 minutes to remove bubbles in the slurry. Thus, five kinds of alumina slurries having different contents of alumina particles were prepared.

Subsequently, the alumina slurry was applied to the entire surface of the 20 mm x 16 mm surface of the test piece, and then the 20 mm x 16 mm side of the other test piece was set in a cross. Here, the clearance between the two test pieces was adjusted to be about 90 占 퐉, and the alumina slurry was previously filled and dried overnight to obtain a joined body. Further, when the alumina slurry had an alumina content of 80% by mass, fluidity was not sufficient and the application to the test piece could not be sufficiently performed, so that a bonded assembly could not be produced.

The bonded assembly was transferred to an atmospheric furnace and calcined at 1650 DEG C for 2 hours with the raised surface of the alumina sintered body placed on the upper side of the bonded body so that the surface pressure of the bonded surface was 0.03 MPa, thereby producing an alumina bonded body. A rod-like test piece having a size of 3 mm x 2 mm x 10 mm was produced from the alumina bonded body thus obtained, and a three-point firing test with a lower span of 8 mm was performed to measure the flexural strength of each of 3 to 4, Respectively. The results are shown in Table 1, and the effect of the alumina content in the alumina slurry was examined based on the above results.

(Review the results)

In Comparative Example 1 in which the alumina content in the alumina slurry was 65.0 mass%, the evaporation amount of water at the time of drying the alumina slurry was large and a large cavity was formed in the joint portion, and the deterioration of the joint strength was apparent. On the other hand, in Comparative Example 3 in which the alumina content in the alumina slurry was 80.0% by mass, the fluidity of the slurry was not sufficient and the thickness of the bonded portion could not be controlled as described above. On the other hand, in Examples 1 and 2 in which the alumina content in the alumina slurry was set to 69.5 mass% and 74.5 mass%, respectively, an alumina bonded body having a flexural strength of about 200 MPa could be produced. However, in Comparative Example 2 in which the alumina content in the alumina slurry was 77.5 mass%, it was possible to produce a bonded body by the production of a bonded body and sintering. However, as shown in Fig. 3, The bending strength was only about 120 MPa. From these results, it can be seen that the alumina content in the alumina slurry is more than 65.0 mass% and less than 77.5 mass% is very suitable.

(Examination of thickness of joint)

An alumina bonded body was produced in the same manner as described above except that the alumina content in the alumina slurry was fixed at 74.5 mass% and the thickness of the joined portions of the bonded bodies was 60 占 퐉, 40 占 퐉 and 36 占 퐉, respectively, And an average value was calculated. The results are shown in Table 2 together with the results of Example 2 (having a thickness of the bonding portion of 90 占 퐉), and the effect of the thickness of the bonding portion was examined based on the above results.

(Review the results)

Sufficient bending strength of 200 MPa or more was obtained even in the alumina bonded bodies of any of Examples 2 to 5 in which the thickness of the bonded portion was in the range of 30 to 90 탆. Further, when the thickness of the joint portion is less than 30 mu m, it is considered that it can not sufficiently cope with the unevenness of the surface to be bonded of the alumina sintered body. Therefore, no alumina joined body having a thickness of the joint portion of less than 30 mu m is produced here.

(Examination of surface pressure on the surface to be bonded at the time of sintering)

The alumina content in the alumina slurry was fixed at 74.5% by mass to prepare a bonded assembly having a thickness of the bonded portion of 90 占 퐉. An alumina bonded body was produced in the same manner as described above except that the pressed bodies of the alumina sintered bodies were placed on each of the bonded bodies so that the surface pressures of the bonded surfaces were 0.015 MPa, 0.008 MPa, and 0 MPa (magnetic weight only) And the average value of the flexural strength was calculated. The results are shown in Table 3 together with the results of Example 2 (the surface pressure of the surface to be bonded being 0.03 MPa) and the effect of surface pressure on the surface to be bonded at the time of sintering Respectively.

(Review the results)

Sufficient flexural strength of 200 MPa or more was obtained in Examples 2 and 6 in which the surface pressure of the bonded surface during sintering was 0.015 MPa or more. On the other hand, in Comparative Examples 4 and 5 in which the surface pressure of the bonded surface during sintering was 0.008 MPa or less, the flexural strength did not reach 200 MPa. From this, it can be seen that it is necessary to load the surface to be bonded with a surface pressure of 0.015 MPa or more at the time of sintering. Further, in the joining of the alumina sintered body having a height of 1 m or more, it is estimated that the surface pressure of the bonded surface obtained by magnetic weight is about 0.04 MPa. Therefore, in joining of such a large sintered body, Alumina bonded body can be obtained.

(Bonding of a larger alumina sintered body)

On the basis of the above examination results, a larger alumina sintered body (block) was used for the bonded material to prepare an alumina bonded body, and a four-point baking test was performed at room temperature and 1200 캜 in the atmosphere. Specifically, a commercial alumina sintered body having an alumina purity of 99.5% or more and a relative density of 99.0% or more was first processed to 40 mm x 13 mm x 20 mm, and a 40 mm x 13 mm surface was machined with # 200 abrasive grindstone Several grinded specimens were prepared. A cell or D305 (trade name) made by Nakagyo Co., Ltd., which mainly contains an ammonium polyacrylate salt as a dispersant, was added to pure water so that the mass ratio was 17: 1, and the mixture was well stirred to prepare a dispersion medium. With respect to this dispersion medium, alumina particles having a purity of 99.8% or more and an average particle diameter of 600 nm were added so as to have a content of 74.5% by mass and stirred to obtain a slurry in which alumina particles were dispersed and mixed in a dispersion medium. The slurry was vacuum degassed for about 2 minutes by using a vacuum pump to remove bubbles in the slurry. Thus, an alumina slurry having a content of alumina particles of 74.5% by mass was prepared.

Subsequently, the alumina slurry was applied to the entire surface of one 40 mm x 13 mm surface of one test piece, and then the 40 mm x 13 mm surface of the other test piece was matched. Here, the clearance between the two test pieces was adjusted to be approximately 90 占 퐉, and the alumina slurry was previously filled and dried overnight to obtain a bonded structure of 40 mm x 13 mm x 40 mm.

The bonded body was transferred to an atmospheric furnace, and a rolling stone of an alumina sintered body was placed on the upper side of the bonded body so that the surface pressure of the bonded surface was 0.03 MPa, and fired at 1650 DEG C for 2 hours to prepare an alumina bonded body. A rod-shaped test piece of 3 mm x 4 mm x 40 mm in accordance with JIS R1601 was prepared from the thus obtained alumina joined body and subjected to a four-point baking test with a lower span of 30 mm and an upper span of 10 mm Respectively. The number of rod-shaped test pieces used for the measurement was set to five in the room temperature baking test and to four in the high temperature baking test in the air at 1200 캜, and the average value was calculated. Table 4 shows the calculation results of the four-point flexural strength at room temperature and 1200 占 폚 in air using a standard test piece of JIS R1601.

As shown in Table 4, the average flexural strength at room temperature of Example 7 produced as described above was as high as the average flexural strength of Example 2 shown in Table 1. From this, it was found that even if the size of the test piece increases, high strength can be exhibited with good reproducibility. According to the theory of strength of ceramics that discusses the relationship between the size of a test piece and its strength, it is generally known that the strength decreases with an increase in the size of the test piece. This is because the probability of presence of large crack defects handling strength is higher for larger specimens than smaller test specimens. However, in this embodiment, it is considered that the coarse defect, which can be considered to deal with the strength, is mainly present in the joint portion. In Examples 2 and 7, the thickness of the joint portion is the same, As a result, it is considered that almost the same high strength can be obtained irrespective of the size of the test piece.

In Example 7, the average flexural strength in the atmosphere at 1200 캜 was as high as 157 MPa. It can be considered that this is because the joint is made of a pure alumina sintered body and does not contain a substance which deteriorates the high-temperature strength such as a glass phase.

(Industrial availability)

INDUSTRIAL APPLICABILITY As described above, the present invention relates to an alumina bonded body and a method of bonding an alumina body. According to the present invention, a bending strength to room temperature of a test piece cut to include a bonded portion is 200 MPa or more, It is possible to provide a bonded body made of high purity alumina having a flexural strength of 100 MPa or more. By using the bonding method of the present invention, it is possible to bond large-sized alumina sintered bodies without requiring a high degree of flatness on the bonded surface, and since the material constituting the bonded portion is only high purity alumina, It is possible to prevent the contamination by the impurity element and to prevent the deterioration of the strength at high temperature. According to this aspect, the present invention is useful as a method for bonding an alumina bonded body of high strength and high purity, which is used in a large-sized manufacturing apparatus member requiring corrosion resistance and heat resistance, and an alumina sintered body for producing the same.

1A: bonded body 1B: alumina bonded body
1a, 1b: alumina sintered body 2: bonding portion (before sintering)
3: bonding portion (after sintering) 20a:
20b: sintered region 20c:
30: Crack

Claims (6)

Wherein the alumina sintered bodies are bonded to each other through a bonding portion, wherein the bonding portion is made of alumina having a thickness of 30 占 퐉 or more, and the hole diameter in the thickness direction of the bonding portion is 40 to 100% coarse independent pores, fine-grained regions containing fine pores having a pore diameter of 5 탆 or less, and dense sintered regions having a relative density of 98% or more. The method according to claim 1,
The bending strength at room temperature measured in accordance with JIS R1601 is 200 MPa or more and the bending strength in air at 1200 DEG C measured in accordance with JIS R1604 is 100 MPa Lt; / RTI > A pipe member made of the alumina bonded body according to claim 1 or 2, wherein the dense alumina sintered bodies having a relative density of 95% or more are bonded to each other through the joining portion. The method of claim 3,
A pipe member used as a constituent member of a rotary kiln used for manufacturing a positive electrode material for a lithium ion secondary battery. A method of bonding an alumina sintered body to which alumina sintered bodies are bonded is characterized in that pure water added with a dispersant is used as a dispersion medium and only alumina particles having a purity of 99.8% or more as solids are added to the dispersion medium. In the alumina slurry, Wherein the alumina slurry is applied to the surface to be bonded of the alumina sintered body and then the alumina slurry is sandwiched between the surfaces to be bonded with the surfaces to be bonded, The bonded body is heated at a temperature of 1300 ° C to 1700 ° C under a load so that the surface pressure of the bonded surface becomes 0.015 MPa or more, The sintered portion is sintered by heat treatment in air, The bonding method of the alumina sintered body for bonding the body. delete

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